1. The Biological Bases of Behavior
Chapter 3
The Biological Bases of Behavior

2. Neurons The Basic Hardware
Neurons are cells that allow communication within the nervous system
Sensory Neurons- carry messages to brain
Motor Neurons- send messages out
Interneurons- everything else

3. Parts Of A Neuron
Soma
Cell Body: Contain cell nucleus, Greek word for body
Dendrites
Receive information from other neurons. Greek word for tree.
Axon
Long thin fiber that transmits signals away from the dendrites and soma to other neurons
Myelin Sheath
Insulating material that encases axons and may speed up the messages
Terminal buttons
At the end of a axon; secrete chemicals called neurotransmitters.
Synapse
Space where information is transmitted from one neuron to another
Information is received at the dendrites- is passed through the soma and along the axon- to the buttons- then transmitted to the dendrites of other cells at meeting points called synapses.

4. Glia (GLUE)
Cells found throughout the nervous system that provide various types of support for neurons.
Account for 50 % of the brain’s volume.
Supply nourishment to neurons, help remove neurons’ waste products, and provide insulation around many axons.
The myelin sheaths are derived from special types of glial cells
Also play a role in the formation of the human embryo
Neuroscientists are trying to figure out what other functions these cells play.
May play an important role in memory formation, Alzheimer’s and schizophrenia.

5. The Neural Impulse
Inside and outside of the neuron are fluids containing electrically charged atoms and molecules called ions.
Positive ions are sodium and potassium and negative ions are chloride ions. They move back and forth over the cell membrane.
When a neuron is not doing anything it is at its resting potential and it has a negative charge.
When a neuron is stimulated, channels in its cell membrane open and positive ions rush in. This creates an action potential and a message will travel along the axon.
The action potential sometimes takes a break and this time period is called the absolute refractory period but it only lasts 1 or 2 milliseconds.
ALL OR NONE: If your neurons are stimulated they will fire no matter what…BUT neurons can convey the strength of the stimulus. They do so by varying the rate at which they fire action potentials. A stronger stimulus will cause a cell to fire more rapidly.
THE ENTIRE PROCESS DESCRIBED ABOVE WILL HAPPEN IN ONLY A FEW THOUSANDTHS OF A SECOND.

6. When messages are transmitted from one neuron to another…the presynaptic neuron sends the signal and the postsynaptic neuron receives the signal.
Neurotransmitters are chemicals that transmit information from one neuron to another.

7. When neurotransmitters and a receptor molecule combine, reactions in the cell membrane cause a postsynaptic potential (PSP), a voltage charge at a receptor site on a postsynaptic cell membrane.
Two types of messages can be sent from cell to cell.
Excitatory PSP is a positive voltage shift that increases the likelihood that the postsynaptic neuron will fire action potentials.
Inhibitory PSP is a negative voltage shift that decreases the likelihood that the postsynaptic neuron will fire action potentials.
If neurotransmitters do not attach to the postsynaptic cell the are reabsorbed into the presynaptic neuron (reuptake)
Video clip

8. Look at the chart of Common Neurotransmitters on page 71 and copy into your notes.
When done…..draw your neuron and try the review questions in your notes.

9. Like the insulation that covers electrical wires myelin
Review glia, neuron, soma, dendrite, axon, myelin, terminal button, synapse
Like a tree, each branch is a telephone wire that carries incoming messages to you Dendrites
Like the insulation that covers electrical wires myelin
Like a silicon chip in a computer that receives and transmits information between input and output devices as well as between other chips. neuron
Like an electrical cable that carries information axon
Like the maintenance personnel who keep things clean and in working order so the operations of the enterprise can proceed glia
Like the nozzle at the end of a hose, from which water is squirted terminal buttons
Like a railroad junction, where two trains meet. synapse

10. Draw two connecting neurons
Label and explain each function

11. Review
1. Sara is holding Scott’s hand during a scary movie. Suddenly she squeezes his hand very hard. When she does this, the neurons in Scott’s hand will
Start to fire at a faster rate
Send stronger signals to his central nervous system
Enter an absolute refractory period
Release more chloride ions
2. An electric potential that increases the likelihood that the postsynaptic neuron will fire is called an
All or nothing potential
Inhibitory postsynaptic potential
Excitatory postsynaptic potential
Excitatory presynaptic potential
3. The neurotransmitter believed to be associated with schizophrenia is
Dopamine
Acetylcholine
Endorphin
serotonin

12. Peripheral Nervous System and the Central Nervous System

14. Peripheral Nervous System
Peripheral Nervous System is made up of all those nerves that lie outside of the brain and spinal cord. Lies just outside the CNS.
Peripheral Nervous System
Autonomic Nervous System
Controls the automatic, involuntary, visceral functions that people don’t think about. Ex- Heart rate, digestion, perspiration.
Made up of nerves that connect to the heart, blood vessels, and glands.
Somatic Nervous System
Made up of nerves that connect to voluntary skeletal muscles and to sensory receptors.
Afferent nerve fibers- carry info IN to the CNS
Efferent nerve fibers- carry info. OUT from the CNS
Sympathetic Division:
Mobilizes the body’s resources for emergencies
Creates the fight or flight response
Parasympathetic Division:
Slows heart rate and brings body back to peace.
Conserves bodily resources

16. Central Nervous System: Brain and Spinal Cord
Protected by the skull and by enclosing sheaths called meninges.
The Cerebrospinal fluid nourishes the brain and provides a protective cushion for it.
Spinal Cord
An extension of the brain that connects the brain to the rest of the body through the peripheral nervous system.
Runs from the base of the brain to just below the level of the waist.
Many forms of paralysis is because of damage to the spinal cord.
The Brain
Weighs only three pounds but is very important.
Enables us to talk, think, remember, plan, create and dream

17. Neuroscientists and their tools!
1. Electroencephalograph (EEG): monitors electrical activity of the brain
Lesioning: destroying part of the brain
Depends on a lot of animal research

18. 3. Electrical Stimulation: sending a weak electric current to the brain in order to stimulate it
4. Transcranial Magnetic Stimulation: creates virtual lesions. Can enhance or depress activity in a specific area of the brain.
5. Brain-Imaging Procedures:
A) CT scan- x-ray of the brain
B) PET scan- shows brain activity- Can study
neurotransmitters
C) MRI scan- provides better pictures than a CT scan.
Has ability to see structure and activity of the brain